1、Designation: D 1608 98 (Reapproved 2003)Standard Test Method forOxides of Nitrogen in Gaseous Combustion Products(Phenol-Disulfonic Acid Procedures)1This standard is issued under the fixed designation D 1608; the number immediately following the designation indicates the year oforiginal adoption or,
2、 in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.
3、1 This test method describes the phenol-disulfonic acidcolorimetric procedure (1)2for the determination of totaloxides of nitrogen nitrous oxide (N2O) excepted in gaseouseffluents from combustion and other nitrogen oxidation pro-cesses.1.2 It is applicable to a concentration range of oxides ofnitrog
4、en as nitrogen dioxide (NO2) of 5 ppm to severalthousand parts per million by volume (four to several thousandmilligrams per dry standard cubic metre).1.3 Since the grab sampling technique used takes a rela-tively small sample over a very short period of time, the resultobtained will be an instantan
5、eous measure of the nitrogenoxides and, therefore, will be representative of the emissionsonly if the gas stream is well mixed and the concentrationconstant with time. Multiple samples are recommended.1.4 The values stated in SI units are to be regarded asstandard. The SI equivalents are in parenthe
6、ses and may beapproximate.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations pr
7、ior to use. (For more specificsafety precautionary information see 8.5 and Section 3.)2. Referenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent WaterD 1356 Terminology Relating to Sampling and Analysis ofAtmospheresD 1357 Practice for Planning the Sampling of the AmbientAtmosphereD
8、 1605 Practices for SamplingAtmospheres forAnalysis ofGases and Vapors33. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology D 1356.4. Summary of Test Method4.1 The gas sample is admitted into an evacuated flaskcontaining an oxidizing absorbing solution
9、consisting of hy-drogen peroxide in dilute sulfuric acid. The oxides of nitrogenare converted to nitric acid by gas phase oxidation due tooxygen in the sample and by the absorbent solution. Theresulting nitrate ion is reacted with phenol disulfonic acid toproduce a yellow compound (the tri-ammonium
10、salt of 6-nitro-1-phenol-2,4-disulfonic acid), which is measured colorimetri-cally. Calibration curves, prepared from samples of knownnitrate content, are used to determine the amount of nitrate inthe sample with results expressed as nitrogen dioxide.5. Significance and Use5.1 This test method provi
11、des a means to measure the totalnitrogen oxides (NOx) content of gaseous emissions for pur-poses such as determining compliance with regulations, study-ing the effect of various abatement procedures on NOxemis-sions, and checking the validity of instrumental measurements.6. Interferences (1, 2)6.1 I
12、norganic nitrates, nitrites, or organic nitrogen com-pounds that are easily oxidized to nitrates interfere with the testmethod and give erroneously high results. The presence ofcertain reducing agents, for example, sulfur dioxide (SO2),may interfere by consuming part of the hydrogen peroxide inthe a
13、bsorbing solution to leave an inadequate amount forreaction with the oxides of nitrogen. Halides lower the results,but interference from halide ion (and lead) are negligible in theconcentration usually encountered in combustion sources.6.2 The role of some of the constituents of combustioneffluents
14、as possible interfering substances has not been thor-oughly investigated.1This test method is under the jurisdiction of ASTM Committee D22 on AirQuality and is the direct responsibility of Subcommittee D22.03 on AmbientAtmospheres and Source Emissions.Current edition approved April 10, 2003. Publish
15、ed June 2003. Originallyapproved in 1958. Last previous edition approved in 1998 as D 1608 98.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document
16、 Summary page onthe ASTM website.3Withdrawn1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.7. Apparatus7.1 The assembled sampling apparatus is shown in Fig. 1.7.2 Barometer, capable of measuring atmospheric pressureto 6250 Pa 62 mm H
17、g.7.3 Bottles, 120-mL or 4-oz, glass or polyethylene, withleak-free noncontaminating caps.7.4 Evaporating Dishes, new condition, unetched borosili-cate glass or porcelain, about 200-mL capacity. Do not useplatinum ware (7).7.5 Mercury Manometer, open-end U-tube, 1 mm or 36 in.with 1-mm or 0.1-in. di
18、visions.NOTE 1An unbreakable, roll-up type is convenient for this applica-tion.7.6 Microburet, 10-mL capacity, with 0.01-mL divisions.7.7 pH Paper, or litmus paper, covering the range from 7 to14 pH.7.8 Sample Collection Flask, CalibratedTwo-litre round-bottom glass flask with a short neck 24/40 sta
19、ndard-taper joint,protected against implosion or breakage with tape or foamedplastic, with known volume.7.9 Sampling Probe, borosilicate glass, approximately6-mm inside diameter, fitted with a 12/5 spherical joint forattachment to the three-way stopcock on the sample collectionflask, provided with a
20、 filter on the inlet end for removal ofparticulate matter, long enough to extend from approximatelyone-third to halfway into the stack or duct (or at least 1 mbeyond inside wall of stacks greater than2mindiameter), andheated or insulated, or both, sufficiently well to preventcondensation of moisture
21、 while purging and sampling.7.10 Spectrophotometer, or filter photometer, capable ofmeasuring absorbance at 405 nm.NOTE 2A wavelength of 400 nm was actually used in the ProjectThreshold tests, but recent work (3, 6, 7) has shown that the absorbancepeak maximum is actually at 405 nm, which is therefo
22、re a better choice.This change should tend to improve the precision and bias of the testmethod.7.11 Squeeze-bulb, rubber, valved for one-way flow to purgesampling probe.7.12 Stirring Rod, polyethylene, to avoid scratching theevaporating dishes.7.13 Stopcock, Three-way, T-bore, with a 24/40 joint for
23、attachment to the sample collection flask, and a 12/5 sphericaljoint for attachment to the sampling probe.7.14 Stopcock Grease, high vacuum, high temperature,inert.7.15 Thermometer, dial-type or glass, with 1C 2F divi-sions and an approximate range from 5 to 50C 25 to 125F.7.16 Vacuum Pump, portable
24、, capable of evacuating thesample collection flask to a pressure of about 2.5 kPa 25 mmHg or less.7.17 Volumetric Flasks, 50, 100, 1000-mL capacity.7.18 Volumetric Pipets, 1, 2, 3, 4, and 5-mL capacity.7.19 Water Bath or Steam Bath, operating at approximately100C 212F (an electric hot plate is not s
25、uitable because ittends to cause spattering and possible loss of sample).8. Reagents8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the
26、 American Chemical Society,where such specifications are available.4Other reagents maybe used provided it can be demonstrated that they are ofsufficiently high purity to permit their use without decreasingthe accuracy of the determination.8.2 Purity of WaterUnless otherwise indicated, referencesto w
27、ater shall be understood to mean reagent water conformingto Type III or better of Specification D 1193. Additionally, thistest method requires water that is nitrate-free as demonstratedby a low-blank absorbance reading (less than 0.002 nm) inSection 5.8.3 Absorbing SolutionDilute 3.0 mL of hydrogen
28、perox-ide (H2O2, 3 %) to 100 mL with sulfuric acid solution (H2SO4,3+997). A fresh solution shall be prepared weekly. Do notexpose to excessive heat or direct sunlight for prolonged time.4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For sugge
29、stions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.FIG. 1 Diagram of Typical Samp
30、ling Apparatus used for Determination of Oxides of Nitrogen by Test Method D 1608D 1608 98 (2003)28.4 Ammonium Hydroxide (sp gr 0.90)Concentrated am-monium hydroxide (NH4OH). A fresh solution shall be used.8.5 Fuming Sulfuric Acid (H2SO4 XSO3), 15 to 18 weight% free sulfur trioxide. CautionHandle wi
31、th care.8.6 Hydrogen Peroxide (3 %)Dilute 10 mL of concen-trated H2O2(30 %) to 100 mL. A fresh solution shall beprepared each time new absorbing solution is prepared.NOTE 3If the strength of the H2O2(30 %) is in doubt, test as follows:Weigh accurately about 5 mL of the H2O2solution and dilute to exa
32、ctly500 mL. To 20 mL of the dilute solution add 20 mL of H2SO4(1+9) andtitrate with 0.1 N potassium permanganate (KMnO4) solution to apermanent pink color. One millilitre of 0.1 N KMnO4solution = 0.001701gofH2O2.8.7 Phenol (C6H5OH), pure white solid.8.8 Phenol Disulfonic Acid SolutionDissolve 25 g o
33、fphenol in 150 mL of concentrated H2SO4(sp gr 1.84) byheating on a steam bath. Cool, add 75 mL of fuming H2SO4(15to 18 % SO3) and heat on the steam bath at 100C 212F for2 h. Cool and store in a dark glass-stoppered bottle. Thesolution should be colorless; it deteriorates on long standing.Discard if
34、a yellow color develops.8.9 Potassium Nitrate (KNO3)Dry in an oven at 105 to110C for 2 h just before preparation of the standard solution.8.10 Potassium Nitrate, Stock Standard Solution (1 mL = 1mg NO2)Dissolve exactly 2.1980 g of dried KNO3in waterand dilute to 1 L in a volumetric flask.8.11 Potass
35、ium Nitrate, Working Standard Solution (1mL = 100 g NO2)Dilute 10 mL of the stock standardpotassium nitrate solution (1 mL = 1 mg NO2) to 100 mL withwater in a volumetric flask.8.12 Sodium Hydroxide Solution (;1N)Slowly add 40 gof sodium hydroxide (NaOH) pellets to 800 to 900 mLof waterin a 2-L beak
36、er with stirring until all pellets are dissolved.Dilute to 1 L with water and mix well. Store in an airtightpolyethylene or polypropylene bottle.8.13 Sulfuric Acid (sp gr 1.84)Concentrated H2SO4, mini-mum assay 95 %.8.14 Sulfuric Acid (3+997)Carefully add 3 mL of con-centrated H2SO4(sp gr 1.84) to w
37、ater and dilute to 1 L.9. Safety Precautions9.1 Cover the glass sample collection flask, which is evacu-ated during the sampling procedure, with tape or foamedplastic to avoid injury in case of implosion or breakage.9.2 The fuming sulfuric acid used in preparing the phenoldisulfonic acid reagent is
38、highly corrosive and fumes in moistair. Wear protective gloves, apron, and face shield, and carryout the reagent preparation in a hood.9.3 Concentrated acids and bases are used throughout thelaboratory procedure. Use care when adding them to othersolutions to avoid overheating and skin contact.10. S
39、ampling10.1 Pipet 25.0 mL of absorbing solution into a calibratedsampling flask and attach the three-way stopcock to the flask(see Note 4) with the T-bore in the purge position. Insert thesampling probe tip from approximately one-third to halfwayinto the stack or duct, or at least 1 m into stacks gr
40、eater than 2m in diameter, in such a way as to prevent leakage of air intothe stack around the probe. Assemble as shown in Fig. 1,making sure that all ground-glass joints have been properlygreased, and that all joints and fittings are tight and leak-free.Turn the flask stopcock to the evacuate posit
41、ion and evacuatethe flask to the incipient boiling of the solution. If the incipientboiling of the solution cannot be seen, this will be indicated onthe manometer by a low and constant reading (usually around2.5 to 4.0 kPa 20 to 30 torr or 0.8 to 1.2 in. Hg. Shut off thepump valve and then the pump.
42、 Check for leakage by observ-ing the manometer for any pressure increase. Any increasegreater than 1.33 kPa 10 torr or 0.4 in. Hg over a 1-minperiod is not acceptable; do not take a sample until the leakageproblem is corrected. Turn the flask stopcock to the purgeposition. Using a pump or a valved r
43、ubber squeeze bulb,thoroughly purge the sampling probe and the flask stopcockwith the sample gas until the probe and stopcock are warmedto the gas temperature and free of condensate. If condensationremains, heat the probe and purge until the condensationdisappears. With the pump valve and pump shut
44、off, turn theflask stopcock to the evacuate position and record the flasktemperature, the difference in mercury levels in the manometer,and the barometric pressure. The absolute pressure in the flaskis equal to the barometric pressure minus the manometerreading. Immediately, turn the stopcock to the
45、 sample positionso that the gas enters the flask and the pressures in the flask andthe sample line are equalized (usually about 15 s are sufficient).Turn the stopcock to the purge position to seal the flask andallow the gas to remain in contact with the absorbing solutionovernight (see Note 5) at ro
46、om temperature. For furtherinformation on sampling, refer to Practice D 1357 and Prac-tices D 1605.NOTE 4The end 6 mm 14 in. of the male 24/40 standard-taper jointis not lubricated to minimize contact of the gas sample with stopcockgrease during absorption.NOTE 5If an overnight absorption period is
47、not feasible, the samplecan be shaken initially and every 20 min for a 2-h period. The result willnot be significantly different than for a static overnight absorption period,provided that the oxygen concentration in the flask is greater than 1 %.11. Calibration11.1 Sample Collection Flask VolumeFil
48、l the sample flaskand stopcock assembly with water up to the stopcock plug.Determine the volume to 610 mL by measuring either thevolume or weight of the water contained in the assembly.Number and record the volume on the flask.11.2 Spectrophotometer CalibrationPrepare a calibrationcurve to cover a r
49、ange from about 0 to 125 ppm NO2, based on2000-mL samples of dry gas at 21C 70F and 101.33 kPa760 torr 29.92 in. Hg. Using a microburet or pipets, transfer0.0, 1.0, 2.0, 3.0, 4.0, and 5.0 mL of the working standardKNO3solution (1 mL = 100 g NO2) into the 200-mL evapo-rating dishes and add 25.0 mL of absorbing solution to each.Proceed in accordance with 12.3 to 12.5. Construct a calibra-tion curve by plotting the absorbencies of the solutions at 405nm against the micrograms of NO2.NOTE 6Higher sample concentrations may
